Abstract: We present an up-to-date review of current knowledge relating nitrogen (N) inputs to ecological effects, from published literature, reports, and some recent unpublished studies. Our goal is to summarize research on ecosystems across the United States. We include N
gradient, long-term, and fertilizer studies; for fertilizer studies, we focus on those with low N additions (i.e., close to ambient deposition). We include both publications that report a response and those that report the lack of response.